AG500 Problem?

Has anyone else had this problem? When running my AG500 into my Epifani T112 cabs( either one or two) the amp goes into protection mode if I play loud, either on the power side with high volume or sudden transients like popping. I know the amp can't support a load below 4 ohms, but the cabs are 8 ohms each. I am open to the possibility that the cabs might be wrong, but I don't know. If anyone has any insight into this, I would appreciate a response.
Peace